Thread: gdb with postgres

On Mon, Jun 6, 2011 at 1:13 PM, HuangQi <huangqiyx@gmail.com> wrote:
> Hi,
>    I was using gdb to debug postgres. In order to debug the backend of
> running query, I start postgres first and use "select * from
> pg_backend_pid()" to ask for backend pid. Then I start gdb in another bash
> window with "gdb postgres" and attach the pid obtained above and set the
> breakpoint. Then I run the query from the first window. However, the
> debugging precess which is shown below is not going to the breakpoint. I
> tried many different breakpoints, but it always start from the 305
> client_read_ended().
>

Please compile with -O0 -g flags to see all the debug symbols.

CFLAGS="-O0 -g" ./configure --enable-debug

Thanks,
Pavan

--
Pavan Deolasee
EnterpriseDB     http://www.enterprisedb.com

Sorry, but recompile with this flag still doesn't work. <br /><br /><div class="gmail_quote">On 6 June 2011 15:46,
PavanDeolasee <span dir="ltr"><<a href="mailto:pavan.deolasee@gmail.com">pavan.deolasee@gmail.com</a>></span>
wrote:<br/><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div
class="im">OnMon, Jun 6, 2011 at 1:13 PM, HuangQi <<a href="mailto:huangqiyx@gmail.com">huangqiyx@gmail.com</a>>
wrote:<br/> > Hi,<br /> >    I was using gdb to debug postgres. In order to debug the backend of<br /> >
runningquery, I start postgres first and use "select * from<br /> > pg_backend_pid()" to ask for backend pid. Then I
startgdb in another bash<br /> > window with "gdb postgres" and attach the pid obtained above and set the<br /> >
breakpoint.Then I run the query from the first window. However, the<br /> > debugging precess which is shown
below isnot going to the breakpoint. I<br /> > tried many different breakpoints, but it always start from the 305<br
/>> client_read_ended().<br /> ><br /><br /></div>Please compile with -O0 -g flags to see all the debug
symbols.<br/><br /> CFLAGS="-O0 -g" ./configure --enable-debug<br /><br /> Thanks,<br /> Pavan<br /><font
color="#888888"><br/> --<br /> Pavan Deolasee<br /> EnterpriseDB     <a href="http://www.enterprisedb.com"
target="_blank">http://www.enterprisedb.com</a><br/></font></blockquote></div><br /><br clear="all" /><br />-- <br
/>BestRegards<br />Huang Qi Victor<br /> 

On Mon, Jun 6, 2011 at 3:43 AM, HuangQi <huangqiyx@gmail.com> wrote:
> Hi,
>    I was using gdb to debug postgres. In order to debug the backend of
> running query, I start postgres first and use "select * from
> pg_backend_pid()" to ask for backend pid. Then I start gdb in another bash
> window with "gdb postgres" and attach the pid obtained above and set the
> breakpoint. Then I run the query from the first window. However, the
> debugging precess which is shown below is not going to the breakpoint. I
> tried many different breakpoints, but it always start from the 305
> client_read_ended().
>
> GNU gdb 6.6
> Copyright (C) 2006 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you are
> welcome to change it and/or distribute copies of it under certain
> conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for details.
> This GDB was configured as "sparc-sun-solaris2.10"...
> (gdb) b qp_add_paths_to_joinrel
> Breakpoint 1 at 0x1a6744: file joinpath.c, line 67.
> (gdb) attach 23903
> Attaching to program `/usrlocal/pgsql/bin/postgres', process 23903
> Retry #1:
> Retry #2:
> Retry #3:
> Retry #4:
> [New LWP 1]
> 0xff0cbaa4 in _rt_boot () from /usr/lib/ld.so.1
> (gdb) n
> Single stepping until exit from function _rt_boot,
> which has no line number information.
> secure_read (port=0x4a7760, ptr=0x455948, len=8192) at be-secure.c:305
> 305                     client_read_ended();
> (gdb) n
> pq_recvbuf () at pqcomm.c:767
> 767                     if (r < 0)
> (gdb) n
> 769                             if (errno == EINTR)
> (gdb) n
> 782                     if (r == 0)
> (gdb) n
> 788                             return EOF;
> (gdb) n
> 791                     PqRecvLength += r;
> (gdb)
> Any one know what is going wrong? BTW, as you can see, the system is
> solaris.

Perhaps you want "c" for "continue" rather than "n" for "next".

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

On Mon, Jun 6, 2011 at 9:47 AM, HuangQi <huangqiyx@gmail.com> wrote:
> If I enter c, gdb will directly finish executing this process and current
> query will finish. Furthermore, if I enter next query, gdb will not debug it
> and stay in continue status.

Hmm, that must mean your breakpoint isn't properly set.

Instead of doing gdb postgres and then using attach, try just doing
gdb -p PIDNAME, then set your breakpoint, then continue.  That's how
I've always done it, anyway...

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

HuangQi <huangqiyx@gmail.com> wrote:
>>> (gdb) b qp_add_paths_to_joinrel
>>> Breakpoint 1 at 0x1a6744: file joinpath.c, line 67.
>>> (gdb) attach 23903
> If I enter c, gdb will directly finish executing this process and
> current query will finish.
Are you absolutely sure that running your query will result in a
call to this function?
-Kevin

<div class="gmail_quote">On 6 June 2011 21:57, Kevin Grittner <span dir="ltr"><<a
href="mailto:Kevin.Grittner@wicourts.gov">Kevin.Grittner@wicourts.gov</a>></span>wrote:<br /><blockquote
class="gmail_quote"style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left:
1ex;"><divclass="im">HuangQi <<a href="mailto:huangqiyx@gmail.com">huangqiyx@gmail.com</a>> wrote:<br /><br
/></div><divclass="im">>>> (gdb) b qp_add_paths_to_joinrel<br /> >>> Breakpoint 1 at 0x1a6744: file
joinpath.c,line 67.<br /> >>> (gdb) attach 23903<br /><br /></div><div class="im">> If I enter c, gdb will
directlyfinish executing this process and<br /> > current query will finish.<br /><br /></div>Are you absolutely
surethat running your query will result in a<br /> call to this function?<br /><font color="#888888"><br /> -Kevin<br
/></font></blockquote></div><br/><br />Thanks guys for your idea. I found the solution. Because after made some change
inpostgres and make them, I didn't stop the server first. Now I stop it and start after reinstall, then using gdb is
justfine. Thanks for your ideas.<br clear="all" /><br />-- <br />Best Regards<br />Huang Qi Victor<br />